Highly enantioselective hydrolyses of syn-3-acetoxy-2-methyl ester and anti-3-acetox.y-Z-methyl esters with lipase "Amano A" and lioase "Amano A-6" isolated from Aspergillus-niger, are described. In the synthetic studies of erythronolide A, it was required to prepare (2R,3R)-2,4-dimethyl-3-hydroxy-4-pentenoate !, and -4-hexenoate 2. 1) As a model study, hoping to develop a general method for the synthesis of optically active erythro-2-methyl-3-hydroxy propionate derivatives, we examined an enantioselective reduction of 2-methyl-3-oxopropionate ;?. having functionality at C-3 position by the use of various yeasts. The desired (2R,3R)-compound 5 was obtained along with C-2 isomer 5_ with excellent optical purity 099% e.e.) in cases where Rl are 2-fury12) and ethoxycarbonyl group.3) Me Mg R,)+,OOMe OH j, R=H Rl&c,,R2 z R$_ + R$_ O 2 5 5 ; R=Et Unfortunately, however, every attempt to synthesize ,l_ and 2 by the above method failed. Since several steps are required for conversion of 2-fury1 or ethoxycarbonyl groups into the desired olefinic functionalities, the present reductive method seemed not to be advisable for the synthesis of !, and Land thus development of other direct methods were desired. Recently, a number of reports have been published for preparation of chiral alcohols via enantioselective hydrolysis of the corresponding esters with microorganisms or enzymes. 4) Particularly, kinetic resolution of (+)-lwith Gliocladium roseum reported by Sih et al. 5) was quite suggestive for us. However, for preparative scale experiments, the use of commercially available, industrialized enzyme is preferable. Recent reports by Kanegafuchi group 6) concerning enzymatic preparation of (S)-5-hydroxymethyl-3-alkyl-2-oxazolidinones, an important intermediate for (S)-B-blockers, represent an excellent example of enzymes being used for large scale production. We now report lipase catalyzed chemo-and enantioselective kinetic resolution of (+)-methyl syn-and anti-2-methyl-3-acetoxy propionate derivative Land 2. The relative configurations of 2-methyl and 3-acetoxy groups in the substrates should be fixed to syn-(+)-6_ or anti-(+)-z. we have previously7) Synthesis of syn-isomers can be achieved without any difficulties since developed that Zn(BH4)2 reduction of the corresponding 3-keto esters produces syn-2-methyl-3-hydroxy esters with high stereoselectivity. Using this technique, compounds (+)-ka,2) b,8) c,') d,cf 7, e,cf 7, fcf 7, were synthesized. Small amounts of anti-isomers produced in these substrates could be removed cleanly by Si02 column chromatography. On the other hand, anti-isomers (+)-7a,b,c had to be prepared by repeated Si02 column chromato--_